The present invention relates to a storage system and a storage system data migration method.
In recent years, the disk capacity of a storage apparatus, which provides a data storage region, has been increased in line with the larger amounts of data being processed by a host computer (hereinafter, “host”). A storage apparatus creates a pool region from a plurality of physical disk storage regions, extracts from this pool region a storage region of a capacity required by a host to create a logical volume, and provides this logical volume to the host. The host writes and reads data to and from this logical volume.
Although there are differences according to the type of data, generally speaking, the utility value of data decreases with the passage of time, and little used data is stored in a logical volume. If an expensive disk is used to create a logical volume utilized by a host, data of little utility value will be wastefully stored in the storage region of an expensive disk, and the cost-effectiveness of the disk will be reduced.
Further, for example, according to the law, there are situations in which data, such as electronic mail and medical data, must be maintained for a fixed period of time or longer, even, for example, when it is low use data. When an expensive disk is used as the storage destination for data to be stored over a long period of time, as described hereinabove, the cost-effectiveness of the disk decreases, and the operational cost of the storage apparatus rises. With this sort of problem in mind, technology for migrating data from an expensive disk to a low-cost disk has been proposed (Japanese Laid-open Patent No. 2000-293317, U.S. Pat. No. 6,108,748, Japanese Laid-open Patent No. 2003-140836, and Japanese Laid-open Patent No. 2003-345522).
In the above-mentioned prior art, data can be moved by copying data from one disk to another disk. A user, for example, selects a migration-source storage apparatus and a migration-destination storage apparatus, and devises a data migration plan for the purpose of improving the cost-effectiveness of a disk, and enhancing the response performance of high-use data. Here, for example, when migration is performed simultaneously to a plurality of associated volumes, as with volumes that form a copy pair, data migration must be completed by maintaining this association as-is.
However, since the state of a storage apparatus changes in various ways, there is no guarantee of achieving results that correspond to the initial data migration plan. For example, in the case of a storage system that is required to operate non-stop 24-hours-a-day, 365-days-a-year, data will be migrated as the storage apparatus is operating. Therefore, data migration is carried out under an environment in which the states of the components of a storage apparatus (controller, cache memory, and so forth) change in various ways.
If a failure of some sort should occur in the migration-destination storage apparatus during data migration, for example, even if data migration processing is capable of continuing at the time the failure occurs, there will be occasions when the results anticipated by the initial data migration plan will not be achievable thereafter due to the secondary effects of the failure. For example, despite the fact that data migration was executed for the purpose of improving response performance, if the load on the data migration-destination storage apparatus rises, there are times when the anticipated response performance cannot be achieved following completion of the data migration. In this case, a user must go to the added trouble of devising a new data migration plan for realizing the initially anticipated response performance, and re-migrating the data.
Further, it is also possible that data migration processing will fail part way through due to the failure that occurred in the migration-destination storage apparatus. In this case as well, just as described hereinabove, a user must create a new data migration plan and carry out data migration processing.
In addition, the migration of data respectively to a plurality of migration-destination storage apparatuses can also be considered, but if data migration to any one of these migration-destination storage apparatuses fails, a user must execute data migration by creating a data migration plan all over again. When carrying out a data migration, a user devises a data migration plan, sets up the storage apparatuses according to this plan, and waits for data copying to be completed. Therefore, carrying out repeated data migrations to the same migration-targeted volume reduces customer satisfaction. Thus, in the prior art, data migration that takes into consideration the fluctuating state of a storage apparatus is not examined, and as such, is not very user-friendly.